solid oxide fuel cell component and a method of manufacturing a solid oxide fuel cell component

ABSTRACT

A solid oxide fuel cell component ( 12 ) comprises a plurality of solid oxide fuel cells ( 24 ) arranged in spaced apart relationship, and in electrical series, on a surface of the porous gas permeable support structure ( 16 ). Each solid oxide fuel cell ( 24 ) comprises a dense gas tight electrolyte member ( 28 ), a porous gas permeable first electrode ( 26 ) and a porous gas permeable second electrode ( 30 ). Each electrolyte ( 28 ) is arranged in contact with a corresponding one of the first electrodes ( 26 ), each second electrode ( 30 ) is arranged in contact with a corresponding one of the electrolytes ( 28 ). Each of the first electrodes ( 26 ) is arranged in contact with the surface of the support structure ( 16 ). The interconnectors ( 32 ), the peripheral seal layer ( 34 ) and the electrolytes ( 28 ) are arranged to encapsulate all of the first electrodes ( 26 ) except for the surfaces of the first electrodes ( 26 ) in contact with the surface of the support structure ( 16 ) to prevent leakage of reactant from the first electrodes ( 16 ).

The present invention relates to a solid oxide fuel cell component andin particular relates to a planar solid oxide fuel cell component.

One known planar solid oxide fuel cell stack is described in Europeanpatent applications EP0668622A1 and EP0673074A1. These describe a planarsolid oxide fuel cell stack comprising a plurality of solid oxideelectrolyte members, each solid oxide electrolyte member having an anodeelectrode on a first surface and a cathode electrode on a secondopposite surface to form a fuel cell. At least one interconnector isprovided to connect the anode electrode of one fuel cell with thecathode electrode of an adjacent fuel cell such that the solid oxidefuel cells are connected in electrical series. The fuel cells arearranged in a plane on one or both sides of a hollow porous gaspermeable support/distribution member, which supplies either fuel to theanode electrodes or oxidant to the cathode electrodes. The electrolytesof these solid oxide fuel cells are of the order of 1 μm to 50 μm, forexample 10 μm.

The main problems with all solid oxide fuel cells are the highmanufacturing costs, poor thermal expansion compliance and limitedoperational temperature range. The poor thermal expansion compliance ofsolid oxide fuel cells makes them intolerant to temperature differencesand to thermal shocks.

A further problem with all solid oxide fuel cells is that the voltagesare less than the Nernst value due to electrochemical and electricallosses in the fuel cells. These losses depend on the current density.The losses are due to activation in the electrodes, diffusion in theelectrodes and porous gas permeable support member,electrolyte/electrode interfacial resistance, current collection in theelectrodes and ionic resistance in the electrolyte. The activationlosses dominate at low currents, the diffusion losses dominate at highcurrents and the resistive losses dominate at intermediate and highcurrents. Losses also arise due to current flow through theinterconnectors.

Also leakage losses through the electrolyte, interconnectors, and aroundthe periphery of the fuel cells gives rise to further losses. Voids andmicro cracks through the components or leakage around the periphery ofthe components impair the electrochemical performance of the fuel cellsin three respects. Firstly there is a loss of current by diffusion orleakage of fuel or oxygen. Secondly there is a loss of voltage due toreduced oxygen partial pressure difference across the electrolytemembrane of the fuel cell. Thirdly there is increased resistance in theanode electrodes due to the nickel electrodes becoming oxidised tonickel oxide.

Other losses may arise due to oxygen ion leakage currents in theinterconnectors and in the support member, if these posses ionicconductivity. Further losses may arise due to spurious fuel cells formedbetween an anode of one fuel cell and the cathode of an adjacent fuelcell if the cathode of one fuel cell contacts the electrolyte of theadjacent fuel cell. The interconnector short-circuits the spurious fuelcell.

Another problem with solid oxide fuel cells is the chemical interactionbetween the substrate and the anode electrode.

Accordingly the present invention seeks to provide a solid oxide fuelcell component which overcomes or at least reduces the problem ofleakage through and around the fuel cells.

Accordingly the present invention provides a solid oxide fuel cellcomponent comprising a porous gas permeable support structure, aplurality of dense non-porous gas tight interconnectors, a densenon-porous gas tight peripheral seal layer and a plurality of solidoxide fuel cells, the solid oxide fuel cells are arranged in spacedapart relationship on a surface of the porous gas permeable supportstructure, the solid oxide fuel cells are arranged in electrical series,

each solid oxide fuel cell comprises a dense non-porous gas tightelectrolyte member, a porous gas permeable first electrode and a porousgas permeable second electrode, each dense non-porous gas tightelectrolyte is arranged in contact with a corresponding one of theporous gas permeable first electrodes, each porous gas permeable secondelectrode is arranged in contact with a corresponding one of the densenon-porous gas tight electrolyte members,

the dense non-porous gas tight interconnectors, the dense non porous gastight peripheral seal layer and the dense non-porous gas tightelectrolyte members are arranged to encapsulate at least one of theporous gas permeable first electrodes except for the surface of theporous gas permeable first electrode facing the surface of the porousgas permeable support structure to reduce leakage of reactant from theat least one porous gas permeable first electrode.

Preferably the dense non-porous gas tight interconnectors, the densenon-porous gas tight peripheral seal layer and the dense non-porous gastight electrolyte members are arranged to encapsulate all of the porousgas permeable first electrodes except for the surfaces of the porous gaspermeable first electrodes facing the surface of the porous gaspermeable support structure to reduce leakage of reactant from theporous gas permeable first electrodes.

Preferably the solid oxide fuel cell stack comprises a dense non-porousgas tight seal, the dense non-porous gas tight electrolyte members andthe dense non-porous gas tight seal are arranged to encapsulate at leastone of the porous gas permeable second electrodes except for the surfaceof the at least one porous gas permeable second electrode remote fromthe dense non-porous gas tight electrolyte members to reduce leakage ofreactant from the at least one porous gas permeable second electrode.

Preferably the dense non-porous gas tight electrolyte members and thedense non-porous seal are arranged to encapsulate all the porous gaspermeable second electrodes except for the surfaces of the porous gaspermeable second electrodes remote from the dense non-porous gas tightelectrolyte members to reduce leakage of reactant from the porous gaspermeable second electrodes.

Each of the porous gas permeable first electrodes is arranged in contactwith the surface of the porous gas permeable support structure.

Preferably each of the porous gas permeable first electrodes is arrangedin contact with the surface of a current collector, each currentcollector is arranged in contact with a porous barrier layer, the porousbarrier layer is arranged in contact with the surface of the porous gaspermeable support structure.

Preferably the at least one interconnector comprises a first layer onthe porous gas permeable support structure, a second layer on the firstlayer and a third layer on the second layer, the first layer is dense,non-porous and is electronically and ionically non conducting, thesecond layer bonds the third layer to the first layer and the thirdlayer is electronically conducting. Preferably the first layer comprisesa ceramic, the second layer comprises lanthanum chromite and the thirdlayer comprises a metal. Preferably the third layer comprises nickel,platinum, palladium, ruthenium, silver, or an alloy two or more of theelements for example an alloy of palladium and nickel or other oxidationresistant metal. Preferably the first layer comprises yttria stabilisedzirconia doped with silicate glass or yttria stabilised zirconia dopedwith calcium chromate such that the barrier layer is ionically nonconducting.

Alternatively the at least one interconnector comprises a first layer onthe porous gas permeable support structure and a second layer on thefirst layer, the first layer is dense, non-porous and is electronicallyand ionically non conducting and the second layer is electronicallyconducting. Preferably the first layer comprises a ceramic and thesecond layer comprises a metal. Preferably the second layer comprisesnickel, platinum, palladium, ruthenium, silver, or an alloy of two ormore of the elements for example an alloy of palladium and nickel.Preferably the first layer comprises yttria-stabilised zirconia.Preferably the first layer comprises yttria stabilised zirconia dopedwith silicate glass or yttria stabilised zirconia doped with calciumchromate such that the first layer is ionically non conducting.

Preferably the dense non-porous gas tight peripheral seal extends aroundthe periphery of the area defined by the porous gas permeable firstelectrodes and the dense non-porous interconnectors.

Preferably the ends of the dense non-porous interconnectors overlap thedense non-porous gas tight peripheral seal. Preferably the edges of thedense non-porous gas tight electrolyte members overlap the densenon-porous gas tight peripheral seal.

Preferably the dense non-porous gas tight peripheral seal comprises afirst layer and a second layer. Preferably the dense non-porous gastight peripheral seal comprises a ceramic. Preferably the densenon-porous gas Light peripheral seal comprises yttria-stabilisedzirconia. Preferably the dense non-porous gas tight peripheral sealcomprises yttria stabilised zirconia doped with silicate glass or yttriastabilised zirconia doped with calcium chromate such that the densenon-porous gas tight seal is ionically non conducting.

Preferably the dense non-porous seal overlaps the dense non-porous gastight peripheral seal. Preferably the dense non-porous seal overlaps theends of the dense non-porous gas tight electrolytes. Preferably thedense non-porous seal overlaps the ends of the dense non-porousinterconnectors. Preferably the dense non-porous seal comprises a glassceramic material.

Preferably the porous gas permeable substrate comprises a ceramic with athermal expansion coefficient matched to that of the dense non-porousgas tight electrolyte member. Preferably the ceramic comprises a mixtureof magnesium aluminate and magnesia. Alternatively the ceramic comprisescalcia-stabilised zirconia.

One end of each dense non-porous gas tight electrolyte member overlapsone of the interconnectors and the second end of each dense non-porousgas tight electrolyte member may be in sealing contact with the surfaceof the porous gas permeable support structure.

Preferably one end of each dense non-porous gas tight electrolyte memberoverlaps one of the interconnectors and the second end of each densenon-porous gas tight electrolyte member overlaps one of theinterconnectors.

Preferably one end of each dense non-porous gas tight electrolyte memberoverlaps one of the interconnectors and the second end of each densenon-porous gas tight electrolyte member abuts one of theinterconnectors.

Preferably one end of each porous gas permeable first electrode overlapsone of the interconnectors.

Alternatively the whole of each porous gas permeable first electrodeoverlaps one of the interconnectors.

The present invention also provides a method of manufacturing a solidoxide fuel cell component comprising a porous gas permeable supportstructure, a plurality of dense interconnectors, a dense non-porous gastight peripheral seal layer and a plurality of solid oxide fuel cells,the solid oxide fuel cells are arranged in spaced apart relationship ona surface of the porous gas permeable support structure, the solid oxidefuel cells are arranged in electrical series,

each solid oxide fuel cell comprises a dense non-porous gas tightelectrolyte member, a porous gas permeable first electrode and a porousgas permeable second electrode, each dense non-porous gas tightelectrolyte is arranged in contact with a corresponding one of theporous gas permeable first electrodes, each porous gas permeable secondelectrode is arranged in contact with a corresponding one of the densenon-porous gas tight electrolyte members,

each of the porous gas permeable first electrodes is arranged facing thesurface of the porous gas permeable support structure, the methodcomprising the steps of:—

(a) forming the porous gas permeable support structure,

(b) depositing a plurality of dense interconnectors and a densenon-porous gas tight peripheral seal layer on the porous gas permeablesupport structure,

(c) depositing a plurality of porous gas permeable first electrodes onthe porous gas permeable support structure,

(d) depositing a plurality of dense non-porous gas tight electrolytemembers on the porous gas permeable first electrodes such that the denseinterconnectors, the dense non peripheral seal layer and the densenon-porous gas tight electrolyte members are arranged to encapsulate atleast one of the porous gas permeable first electrodes except for thesurface of the porous gas permeable first electrode facing the surfaceof the porous gas permeable support structure to reduce leakage ofreactant from the at least one porous gas permeable first electrode,

(e) depositing a plurality of porous gas permeable second electrodes onthe plurality of dense non-porous gas tight electrolyte members.

Preferably step (d) comprises depositing the plurality of densenon-porous gas tight electrolyte members on the porous gas permeablefirst electrodes such that the dense non-porous interconnectors, thedense non-porous gas tight peripheral seal layer and the densenon-porous gas tight electrolyte members are arranged to encapsulate allof the porous gas permeable first electrodes except for the surfaces ofthe porous gas permeable first electrodes in contact with the surface ofthe porous gas permeable support structure to reduce leakage of reactantfrom the porous gas permeable first electrodes.

Preferably the method comprises the subsequent step of:—

(f) depositing a dense non-porous seal around the plurality of porousgas permeable second electrodes such that the dense non-porous gas tightelectrolytes and the dense non porous seal encapsulate at least one ofthe porous gas permeable second electrodes except for the surface of theat least one porous gas permeable second electrode remote from the densenon-porous gas tight electrolyte members to reduce leakage of reactantfrom the at least one porous gas permeable second electrode.

Preferably step (f) comprises depositing the dense non-porous sealaround the plurality of porous gas permeable second electrodes such thatthe dense non-porous gas tight electrolyte members and the densenon-porous seal encapsulate all the porous gas permeable secondelectrodes except for the surfaces of the porous gas permeable secondelectrodes remote from the dense non-porous gas tight electrolytemembers to reduce leakage of reactant from the porous gas permeablesecond electrodes.

Preferably step (a) comprises depositing the dense non-porous gas tightperipheral seal such that it extends around the periphery of the areadefined by the porous gas permeable first electrodes and the densenon-porous interconnectors.

Preferably step (a) comprises depositing the dense non porousinterconnectors such that they overlap the dense non-porous gas tightperipheral seal.

Preferably step (d) comprises depositing the dense non-porous gas tightelectrolyte members such that they overlap the dense non-porous gastight peripheral seal.

Preferably step (a) comprises depositing a first layer and a secondlayer to form the dense non-porous gas tight peripheral seal. Preferablythe dense non-porous gas tight peripheral seal comprises a ceramic.Preferably the dense non-porous gas tight peripheral seal comprisesyttria-stabilised zirconia.

Preferably step (f) comprises depositing the dense non-porous seal suchthat it overlaps the dense non-porous gas tight peripheral seal.Preferably step (f) comprises depositing the dense non-porous seal suchthat it overlaps the ends of the dense non-porous gas tight electrolytemembers. Preferably step (f) comprises depositing the dense non-porousseal such that it overlaps the ends of the dense non-porousinterconnectors.

Preferably step (d) comprises depositing the dense non-porous gas tightelectrolyte members such that one end of each dense non-porous gas tightelectrolyte member overlaps one of the interconnectors and the secondend of each dense non-porous gas tight electrolyte member is in sealingcontact with the surface of the porous gas permeable support structure.

Step (d) may comprise depositing the dense non-porous gas tightelectrolyte members such that one end of each dense non-porous gas tightelectrolyte member overlaps one of the interconnectors and the secondend of each dense non-porous gas tight electrolyte members abut one ofthe interconnectors.

Alternatively step (d) may comprise depositing the dense non-porous gastight electrolyte members such that one end of each dense non-porous gastight electrolyte member overlaps one of the interconnectors and thesecond end of each dense non-porous gas tight electrolyte memberoverlaps one of the interconnectors.

Preferably step (c) comprises depositing the porous gas permeable firstelectrodes such that one edge of each porous gas permeable firstelectrode overlaps one of the interconnectors.

Alternatively step (c) comprises depositing the porous gas permeablefirst electrodes such that the whole of each porous gas permeable firstelectrode overlaps one of the interconnectors.

Preferably the method comprises the additional steps of:—

(g) sintering after step (d) and before step (e) and

(h) sintering after step (f).

Alternatively the method comprises the additional steps of:—

(g) sintering after step (b) and before step (c),

(h) sintering after step (d) and before step (e), and

(i) sintering after step (f).

Alternatively the method comprises the additional steps of:—

(g) sintering after step (a) and before step (b),

(h) sintering after step (b) and before step (c),

(i) sintering after step (c) and before step (d),

(j) sintering after step (d) and before step (e),

(k) sintering after step (e) and before step (f), and

(l) sintering after step (f).

The present invention will be more fully described by way of examplewith reference to the accompanying drawings in which:—

FIG. 1 is a partially cut away perspective view of a solid oxide fuelcell stack according to the present invention.

FIG. 2 is a plan view of one component of the solid oxide fuel cellstack shown in FIG. 1.

FIG. 3 is an enlarged cross-sectional view along line A-A through thecomponent of the solid oxide fuel cell stack shown in FIG. 2.

FIG. 4 is a cross-sectional view along line B-B through the component ofthe solid oxide fuel cell stack shown in FIG. 3.

FIG. 5 is a cross-sectional view along line C-C through the solid oxidefuel cell component shown in FIG. 3.

FIGS. 6A to 6E illustrate the manufacturing sequence for making thesolid oxide fuel cell stack component shown in FIGS. 3 to 5.

FIG. 7 is a further enlarged cross-sectional view through the solidoxide fuel cell component shown in FIG. 3.

FIG. 8 is an alternative enlarged cross-sectional view along line A-Athrough the solid oxide fuel cell component shown in FIG. 2.

FIG. 9 is a further enlarged cross-sectional view through the solidoxide fuel cell component shown in FIG. 8.

FIG. 10 is a further enlarged cross-sectional view along line A-Athrough the solid oxide fuel cell component shown in FIG. 2.

FIG. 11 is a further enlarged cross-sectional view through the solidoxide fuel cell component shown in FIG. 10.

A solid oxide fuel cell stack 10 according to the present invention isshown in FIGS. 1 to 5 and 7. The solid oxide fuel cell stack 10comprises at least one, preferably a plurality of components 12 arrangedwithin a casing 14. Each component 12, as shown more clearly in FIGS. 2to 5, comprises a hollow porous gas permeable support structure 16 whichhas an internal surface 18 and an external surface 22. The internalsurface 18 of the hollow porous gas permeable support structure 16 atleast partially defines one or more chambers 20 for the supply of afirst reactant to the internal surface 18 of the porous gas permeablesupport structure 16. The external surface 22 of the hollow porous gaspermeable support structure 16 supports a plurality of solid oxide fuelcells 24 which are arranged in spaced apart relationship on the externalsurface 22 of the hollow porous gas permeable support structure 16. Asecond reactant is supplied to the external surface 22 of the hollowporous gas permeable support structure 16. The solid oxide fuel cells 24are electrically interconnected in series.

Each solid oxide fuel cell 24, as shown more clearly in FIGS. 3, 4, 5and 7 comprises a porous gas permeable first electrode 26, a densenon-porous gas tight electrolyte member 28 and a porous gas permeablesecond electrode 30. A plurality of dense non-porous gas tightinterconnectors 32 are provided. At least one, all except two of the,dense non-porous gas tight interconnector 32 is arranged to interconnectthe first electrode 26 of one solid oxide fuel cell 24 with the secondelectrode 30 of an adjacent solid oxide fuel cell 24. Each densenon-porous gas tight interconnector 32 is arranged on the externalsurface 22 of the porous gas permeable support structure 16, most of thedense non-porous gas tight interconnectors 32 are positioned in thespace between two adjacent solid oxide fuel cells 24.

Referring to FIGS. 2 and 3, a dense non-porous gas tight interconnector32A is arranged at a first end of the solid oxide fuel cell stack tointerconnect the porous gas permeable first electrode 26 of one solidoxide fuel cell 24 with a first terminal 36. A dense non-porous gastight interconnector 32B is arranged at a second end of the solid oxidefuel cell stack to interconnect the porous gas permeable secondelectrode 30 of one solid oxide fuel cell 24 with a second terminal 37.

The porous gas permeable first electrode 26 of each solid oxide fuelcell 24 is arranged on the external surface 22 of the porous gaspermeable support structure 16, as shown in FIGS. 3, 4, 5 and 7.

A dense non-porous gas tight peripheral seal layer 34 is arranged on theexternal surface 22 of the porous gas permeable support structure 16 onthe periphery of the area defined by the porous gas permeable firstelectrodes 26 and the dense non-porous gas tight interconnectors 32, 32Aand 32B.

A first end 26A of each porous gas permeable first electrode 26 isarranged to contact one of the dense non-porous gas tightinterconnectors 32. A second end 26B of each porous gas permeable firstelectrode 26 is arranged in spaced part relationship with an adjacentone of the dense non-porous gas tight interconnectors 32.

Each dense non-porous gas tight electrolyte 28 is arranged in contactwith a corresponding one of the porous gas permeable first electrodes26. A first end 28A of each dense non-porous gas tight electrolyte 28 isarranged in sealing contact with one of the dense non-porous gas tightinterconnectors 32. A second end 28B of each dense non-porous gas tightelectrolyte 28 is arranged between the second end 26B of the porous gaspermeable first electrode 26 and the adjacent one of the densenon-porous gas tight interconnectors 32. The second end 28B of the densenon-porous gas tight electrolyte member 28 is in sealing contact withthe external surface 22 of the porous gas permeable support structure16. The second end 28B of each dense non-porous gas tight electrolyte 28is also in sealing contact with the adjacent one of the dense non-porousgas tight interconnectors 32. The edges 28C and 28D of each densenon-porous gas tight electrolyte 28 are in sealing contact with thedense non-porous gas tight peripheral seal layer 34 to encapsulate theporous gas permeable first electrodes 26 to prevent gas leakage from theporous gas permeable first electrodes 26.

Each porous gas permeable second electrode 30 is arranged in contactwith a corresponding one of the dense non-porous gas tight electrolytes28. A first end 30A of each porous gas permeable second electrode 30 isspaced from a second end 30B of an adjacent porous gas permeable secondelectrode 30. The second end 30B of each porous gas permeable secondelectrode 30 is arranged in contact with the adjacent one of the densenon-porous gas tight interconnectors 32.

It is to be noted that the second end 30B of the porous gas permeablesecond electrode 30 of each solid oxide fuel cell 24 is spaced from thedense non-porous gas tight electrolyte 28 of an adjacent solid oxidefuel cell 24 to prevent the formation of spurious solid oxide fuelcells.

A dense non-porous gas tight seal 38 is arranged between the porous gaspermeable second electrodes 30 and is in sealing contact with a portionof the dense non-porous gas tight electrolytes 28 and the densenon-porous gas tight interconnectors 32. The dense non-porous gas tightseal 38 is also arranged around the periphery of the area defined by theporous gas permeable second electrodes 30 and is in sealing contact withthe dense non-porous gas tight peripheral seal layer 34. Thus the porousgas permeable second electrodes 30 are encapsulated to prevent gasleakage from the porous gas permeable second electrodes 30.

The dense non-porous gas tight seal 38 penetrates into the edges of theporous gas permeable second electrodes 30 which contact the edges of thedense non-porous gas tight electrolyte 28 and the edges of the surfaceof the dense non-porous gas tight interconnector 32. The infiltration ofthe dense non-porous gas tight seal 38 into the edges of the porous gaspermeable second electrodes 30 forms a further seal in the event of aleakage of gas from the porous gas permeable first electrodes 26 throughthe dense non-porous gas tight interconnectors 32.

The porous gas permeable support structure 16 preferably comprisesmagnesia doped magnesium aluminate, however calcia stabilised zirconiaor other suitable ceramics may be used. The magnesium aluminate ispreferred because it is cheaper and has lower density than calciastabilised yttria, and additionally the magnesium aluminate hasnegligible ion conductivity. The magnesium aluminate is doped withmagnesia to match the thermal expansion coefficient of the yttriastabilised zirconia electrolyte, thus the magnesia doped magnesiumaluminate is produced by mixing 60-70 wt % magnesia and balance alumina.The calcia-stabilised zirconia must have a dopant level of greater than16 mol % calcia to ensure the zirconia is fully stabilised, for example7 wt % calcia. One advantage of calcia stabilised zirconia is that ithas a thermal expansion coefficient matched to the dense non-porous gastight electrolytes. The calcia stabilised zirconia does not react withthe other components of the fuel cells during sintering and the calciastabilised zirconia has a lower oxygen ion conductivity than yttriastabilised zirconia.

Each dense non-porous gas tight interconnector 32, 32A and 32B comprisesthree layers. The first layer 40, on the porous gas permeable supportstructure, is a dense non-porous gas tight barrier layer which isneither ionically conducting or electronically conducting and forexample comprises yttria stabilised zirconia containing a dopant, forexample 1-2 wt % silicate glass material or 0.02-4 wt % calciumchromate. The dopants reduce the oxygen ion conductivity and act assintering aids. The second layer 42 is a bond coating for the thirdlayer and for example comprises lanthanum chromate. The second layerimproves the densification of the first layer and reduces the ionicconductivity of the first layer The second layer is about 10 μm thickafter sintering. The third layer 44 is electronically conducting andoxidation resistant and comprises nickel, platinum, palladium,ruthenium, silver or an alloy of any two or more of nickel, platinum,palladium, ruthenium and silver, for example an alloy of palladium andnickel or other suitable metal. The platinum is sintered into thelanthanum chromite such that about 50% of the surface area of theinterconnector is platinum and about 50% is lanthanum chromite.

Alternatively each interconnector 32, 32A, 32B comprises a first layer,on the porous gas permeable support structure, and a second layer on thefirst layer. The first layer is dense non-porous gas tight and iselectronically and ionically non-conducting and the second layer iselectronically conducting. Preferably the first layer comprises aceramic and the second layer comprises a metal. Preferably the metalcomprises nickel, platinum, palladium, ruthenium, silver or an alloy ofany two or more of nickel, platinum, palladium, ruthenium and silver,for example an alloy of 80 wt % palladium and 20 wt % nickel or otheroxidation resistant metal.

The first layer 40 of the interconnectors 32, 32A and 32B may bedeposited in two layers such that the yttria stabilised zirconia anddopants firstly fills the pores in the hollow porous gas permeablesupport structure 16 and then produces a smooth pore free surface.

The dense non-porous gas tight peripheral seal layer 34 is a densenon-porous gas tight barrier layer which is neither ionically conductingor electronically conducting and for example comprises yttria stabilisedzirconia containing a dopant, for example 1-2 wt % silicate glassmaterial or 0.02-4 wt % calcium chromate. The dopants reduce oxygenionic conductivity and act as sintering aids. The dense non-porous gastight barrier peripheral seal 34 may be deposited in two layers suchthat the yttria stabilised zirconia firstly fills the pores in thehollow porous gas permeable support structure 16 and then produces asmooth pore free surface.

The first electrode, anode, 26 comprises 60 wt % nickel oxide and 40 wt% yttria stabilised zirconia. The yttria-stabilised zirconia comprises 8wt % yttria. The sintered anode thickness is about 30 μm. It the hollowporous gas permeable support structure 16 comprises magnesia dopedmagnesium aluminate a barrier layer is deposited on to the hollow porousgas permeable support structure 16 before the first electrode 26,because the nickel oxide reacts with the alumina in the magnesiumaluminate. The barrier layer must layer prevent this reaction occurringand must be porous to allow reactants to flow to and from the anode 26.Preferably the barrier layer comprises 8 wt % yttria stabilisedzirconia.

Alternatively the porous gas permeable first electrode, anode, 26comprises nickel, palladium and ceria. The porous gas permeable firstelectrode 26 may comprise ceria, a ceria/nickel or palladium cement, orceria with an electronic conducting current distribution mesh of nickelor palladium or nickel/palladium alloy.

The dense non-porous gas tight electrolytes 28 comprise 8 wt % yttriastabilised zirconia and an oxide to aid sintering. The oxide may be 1 wt% alumina, 1 mol % alumina and 1 mol % titania, 5 mol % titania, 1 wt %nickel oxide or 0.25 wt % boron oxide. The dense non-porous gas tightelectrolytes 28 have a density of greater than 98%. The electrolytes 28may comprise yttria stabilised zirconia with two different particlesizes, for example an average particle size of about 0.7 micrometers andan average particle size of about 0.1 micrometers to enable goodsintering to obtain maximum density without shrinkage and delaminationof the electrolytes 28. The thickness of the dense non-porous gas tightelectrolytes 28 is about 10 μm.

The porous gas permeable second electrode, cathode electrode, 30comprises a first layer and a second layer. The first layer comprises 50wt % 8 wt % yttria stabilised zirconia and 50 wt % lanthanum strontiummanganite (La_(0.8) Sr_(0.15) MnO₃). The mixture of yttria stabilisedzirconia and lanthanum strontium manganite provides enhanced oxygen ionconductivity for the first layer, increasing the effective area of theporous gas permeable second electrode 30/dense non-porous gas tightelectrolyte 28 interface. This improves oxygen reduction kinetics,reducing the cathode polarisation loss. The first layer is between 5 and15 μm thick. The second layer comprises 100 wt % lanthanum strontiummanganite having a larger particle size than the first layer. The secondlayer improves the electronic conductance of the second electrode 30.The larger particle size improves the lateral conductivity and sinteringcharacteristics to produce a porous crack free second electrode 30. Thesecond layer is between 50 and 150 μm thick. The porous gas permeablesecond, cathode, electrode 30 may comprise lanthanum strontiummanganite/ceria composite.

The dense non-porous gas tight seal 38 comprises a glass ceramic forexample a barium oxide silica alumina based glass material whichcontains zircon which forms a glass ceramic film. Other suitable glassceramics may be used.

The terminals 36 and 37 comprise nickel aluminide, and are formed byplacing an aluminium layer on the substrate 16 and placing a nickel lugin contact with the aluminium layer. The aluminium and nickel react atthe sintering temperature to form nickel aluminide to bond the terminal36, 37 to the lug and the interconnector 32A, 32B. Alternatively theterminals 36 and 37 comprise 80 wt % palladium and 20 wt % nickel.

The solid oxide fuel cell component is manufactured by forming theporous gas permeable support structure 16 by producing a ceramic doughof the calcia stabilised zirconia, or magnesia doped magnesiumaluminate, by mixing powdered ceramic with an aqueous organic matrix.

The ceramic dough is then passed through a ram extruder using a die toproduce the porous gas permeable support structure shown in FIGS. 3, 4and 5 although other shapes may be produced. After extrusion the porousgas permeable support structure 16 is dried for a suitable period oftime. Microwave or others suitable drying may be used to accelerate thedrying process.

The dried porous gas permeable support structure 16 is machined bycutting, grinding, milling, linishing and drilling using conventionaltools. The machining is used to form manifolds, or interconnections, atthe ends of the porous gas permeable support structure 16. The ends ofthe porous gas permeable support structure 16 may be sealed with a capof the dried extruded ceramic dough and or a paste of the ceramic doughand dried.

The porous gas permeable support structure 16 is then sintered in afurnace on zirconia balls, which allow movement of the porous gaspermeable support structure 16. The porous gas permeable supportstructure is sintered at a temperature of 1400° C. for a suitable time,for example two hours, to allow the temperature of the porous gaspermeable support structure 16 to become equal at all points. Thisenables uniform sintering of the porous gas permeable support structure16.

A plurality of first layers 40 of dense non-porous barrier layer of thedense non-porous gas tight interconnectors 32 and the dense non-porousgas tight peripheral seal layer 34 are deposited on the porous gaspermeable support structure 16, as shown in FIG. 6A. Initially a basecoat of calcia stabilised zirconia, or other suitable ceramic, isapplied by dip coating to fill in the porosity of the porous gaspermeable support structure 16, the calcia stabilised zirconia has aparticle size less than 2 μm and is applied as a water based slurry. Thebase coat is then fired at 1400° C. for 1 hour. Then the topcoat isapplied by screen-printing using a common screen, the topcoat isyttria-stabilised zirconia comprising a dopant as discussed previously.

A plurality of second layers 42 and third layers 44 of the densenon-porous gas tight interconnectors 32 are deposited on the firstlayers 40 of the dense non-porous gas tight interconnectors 32 as shownin FIG. 6B. The second layers 42 and third layers 44 overlap the densenon-porous gas tight peripheral seal layer 34. The second and thirdlayers 42 and 44 of the dense non-porous gas tight interconnectors 32are deposited by screen-printing.

A plurality of porous gas permeable first electrodes 26 are deposited onthe porous gas permeable support structure 16. The porous gas permeablefirst electrodes 26 overlap one of the adjacent dense non-porous gastight interconnectors 32 but are spaced from the other of the adjacentdense non-porous gas tight interconnectors 32, as shown in FIG. 6C. Theporous gas permeable first electrodes 26 are deposited byscreen-printing.

A plurality of dense non-porous gas tight electrolytes 28 are depositedon the porous gas permeable first electrodes 26 such that the densenon-porous gas tight interconnectors 32, the dense non-porous gas tightperipheral seal layer 34 and the dense non-porous gas tight electrolytes28 are arranged to encapsulate all of the porous gas permeable firstelectrodes 26, as shown in FIG. 6D, except for the surface of the porousgas permeable first electrodes 26 in contact with the surface of theporous gas permeable support structure 16 to reduce, preferably prevent,leakage of reactant from the porous gas permeable first electrodes 26.The dense non-porous gas tight electrolytes 28 overlap the densenon-porous gas tight peripheral seal layer 34. Each dense non-porous gastight electrolyte 28 overlaps one dense non-porous gas tightinterconnector 32 and abuts the other dense non-porous gas tightinterconnector 32. The dense non-porous gas tight electrolytes 28 aredeposited by screen-printing. The electrolytes 28 may be deposited bydepositing a layer comprising yttria stabilised zirconia particles withthe average particle size of about 0.7 micrometers which produces 98%density. A second layer may be deposited by depositing a mixture ofyttria stabilised zirconia particles with an average particle size of0.7 micrometers and yttria stabilised zirconia particles with an averageparticle size of 0.1 micrometers.

A plurality of porous gas permeable second electrodes 30 are depositedon the plurality of dense non-porous gas tight electrolytes 28, as shownin FIG. 6E. The porous gas permeable second electrodes 30 overlap thedense non-porous gas tight interconnectors 32. The porous gas permeablesecond electrode 30 of each solid oxide fuel cell is spaced from thedense non-porous gas tight electrolyte 28 of an adjacent solid oxidefuel cell to prevent the formation of spurious solid oxide fuel cells.The porous gas permeable second electrodes 30 are deposited by stencilprinting, or slurry spraying, to minimise damage to the underlying densenon-porous gas tight electrolytes 28.

The dense non-porous gas tight seal 38 is deposited around the pluralityof porous gas permeable second electrodes 30 such that the densenon-porous gas tight electrolytes 28 and the dense non-porous gas tightseal layer 38 encapsulates all the porous gas permeable secondelectrodes 30 except for the surfaces of the porous gas permeable secondelectrodes 30 remote from the dense non-porous gas tight electrolytes28. This reduces, preferably prevents, leakage of second reactant fromthe porous gas permeable second electrodes 30 to the porous gaspermeable first electrodes 26 and reduces, preferably prevents, leakageof first reactant from the porous gas permeable first electrodes 26 tothe porous gas permeable second electrodes 30. The dense non-porous gastight seal 38 is deposited by screen-printing.

There may be a sintering step after the dense non-porous gas tightperipheral seal layer 34, dense non-porous gas tight interconnectors 32,porous gas permeable first electrodes 26 and dense non-porous gas tightelectrolytes 28 have been deposited. There may be a further sinteringstep after the porous gas permeable second electrodes 30 and densenon-porous seal 38 has been deposited.

Alternatively there may be a sintering step after the dense non-porousgas tight peripheral seal layer 34 and dense non-porous gas tightinterconnectors 32 have been deposited There may be a further sinteringstep after the porous gas permeable first electrodes 26 and densenon-porous gas tight electrolytes 28 have been deposited and a furthersintering step after the porous gas permeable second electrodes 30 anddense non-porous gas tight seal 38 has been deposited.

Alternatively there may be a sintering step after each one of the densenon-porous gas tight peripheral seal layer 34, the dense non-porous gastight interconnectors 32, the porous gas permeable first electrodes 26,the dense non-porous gas tight electrolytes 28, the porous gas permeablesecond electrodes 30 and the dense non porous gas tight seal 38 has beendeposited.

The sintering steps comprise heating to temperatures between 1000° C.and 1500° C. The interconnectors 32 are sintered at a temperature in therange 1300° C. to 1500° C., the anode electrodes 26 and electrolytes 28are sintered at a temperature in the range the 1400° C. to 1450° C. andthe cathode electrodes 30 are sintered at a temperature in the range1000° C. to 1400° C.

The arrangement allows the dense non-porous gas tight interconnectors 32and dense non-porous gas tight peripheral seal layer 34 to be sinteredat high temperatures to make them dense, non-porous and gas tightwithout unwanted chemical reactions with other layers. Thus thesintering temperature is reduced as each layer is deposited.

It is to be noted that the porous gas permeable support structure 16 hastwo parallel planar surfaces and that one or both of the planar surfacesmay be provided with solid oxide fuel cells.

A cross-section through an alternative solid oxide fuel cell component112, is shown more clearly in FIGS. 8 and 9. The component 112 comprisesa hollow porous gas permeable support structure 116, which has aninternal surface 118 and an external surface 122. The internal surface118 of the hollow porous gas permeable support structure 116 at leastpartially defines one or more chambers 120 for the supply of a firstreactant to the internal surface 118 of the porous gas permeable supportstructure 116. The external surface 122 of the hollow porous gaspermeable support structure 116 supports a plurality of solid oxide fuelcells 124 which are arranged in spaced apart relationship on theexternal surface 122 of the hollow porous gas permeable supportstructure 116. A second reactant is supplied to the external surface 122of the hollow porous gas permeable support structure 16. The solid oxidefuel cells 124 are electrically interconnected in series.

Each solid oxide fuel cell 124 comprises a porous gas permeable firstelectrode 126, a dense non-porous gas tight electrolyte member 128 and aporous gas permeable second electrode 130. A plurality of densenon-porous gas tight interconnectors 132 are provided. At least one, allexcept two of the, dense non-porous gas tight interconnector 132 isarranged to interconnect the porous gas permeable first electrode 126 ofone solid oxide fuel cell 124 with the porous gas permeable secondelectrode 130 of an adjacent solid oxide fuel cell 124.

The porous gas permeable first electrode 126 of each solid oxide fuelcell 124 is arranged on a respective one of a plurality of porous gaspermeable current collectors 135. Each porous gas permeable currentcollector 135 is arranged on a respective one of a plurality of porousgas permeable barrier layers 123. Each dense non-porous gas tightinterconnector 132 comprises a dense non-porous gas tight barrier layer134 on the surface 122 of the porous gas permeable support structure 116and an electronically conducting and oxidation resistant layer 133 onthe dense non-porous gas tight barrier layer 134. The dense non-porousgas tight barrier layer 134 and the porous gas permeable barrier layer123 prevent chemical interactions between the porous gas permeable firstelectrode 126 and the porous gas permeable support structure 116. Mostof the dense non porous gas tight interconnectors 132 are positioned inthe space between two adjacent solid oxide fuel cells 124. A densenon-porous gas tight interconnector 132A is arranged at one end of thesolid oxide fuel cell component to interconnect the porous gas permeablefirst electrode 126 of one solid oxide fuel cell 124 with a firstterminal 36. A dense non-porous gas tight interconnector 132B isarranged at one end of the solid oxide fuel cell component tointerconnect the porous gas permeable second electrode 130 of one solidoxide fuel cell 124 with a second terminal 37.

The dense non-porous gas tight peripheral seal layer 134 is arranged onthe external surface 122 of the porous gas permeable support structure116 on the periphery of the area defined by the porous barrier layer123.

The whole of one surface, the surface remote from the dense non-porousgas tight electrolyte member 128, of each porous gas permeable firstelectrode 126 is arranged to contact the respective current collector135.

Each dense non-porous gas tight electrolyte 128 is arranged in contactwith a corresponding one of the porous gas permeable first electrodes126. A first end 128A of each dense non-porous gas tight electrolyte 128is arranged in sealing contact with the dense non-porous barrier layer134 of a dense non-porous gas tight interconnector 132. A second end128B of each dense non-porous gas tight electrolyte 128 is arranged insealing contact with layer 133 of the respective dense non-porous gastight interconnector 132. The edges 128C and 128D of each densenon-porous gas tight electrolyte 128 are in sealing contact with thedense non-porous gas tight peripheral seal layer 134 to encapsulate theporous gas permeable first electrodes 126 to prevent gas leakage fromthe porous gas permeable first electrodes 126.

Each porous gas permeable second electrode 130 is arranged in contactwith a corresponding one of the dense non-porous gas tight electrolytes128. A first end 130A of each porous gas permeable second electrode 130is spaced from a second end 130B of an adjacent porous gas permeablesecond electrode 130. The second end 130B of each porous gas permeablesecond electrode 130 is arranged in contact with the adjacent one of theinterconnectors 132. The second end 130B of each porous gas permeablesecond electrode 130 is spaced from the dense non-porous gas tightelectrolyte 128 of an adjacent fuel cell 124 to prevent the formation ofspurious solid oxide fuel cells.

A dense non-porous gas tight seal 138 is arranged between the porous gaspermeable second electrodes 130 and is in sealing contact with a portionof the dense non-porous gas tight electrolytes 128. The dense non-porousgas tight seal 138 is also arranged around the periphery of the areadefined by the porous gas permeable second electrodes 130 and is insealing contact with the dense non-porous gas tight peripheral seallayer 134. The dense non-porous gas tight peripheral seal layer 134 isalso in sealing contact with the interconnectors 132. Thus the porousgas permeable second electrodes 130 are encapsulated to prevent gasleakage from the porous gas permeable second electrodes 130.

The dense non-porous gas tight seal 138 penetrates into the edges of theporous gas permeable second electrodes 130, which contact the edges ofthe dense non-porous gas tight electrolyte member 128, and the surfaceof layer 133 of the dense non-porous gas tight interconnectors 132 thatis not contacted by the dense non-porous gas tight electrolyte member128 and not contacted by the porous gas permeable second electrodes 130.The infiltration of the dense non-porous gas tight seal 138 into theedges of the porous gas permeable second electrodes 130 forms a furtherseal in the event of a leakage of gas from the porous gas permeablefirst electrodes 126 through the dense non-porous gas tightinterconnectors 132.

This arrangement is produced by firstly depositing the porous gas tightbarrier layer 123 and the dense non-porous gas tight peripheral barrierlayer 134. Then secondly the layer 133 of the interconnectors 132 andcurrent collectors 135 are deposited and the assembly is sintered athigh temperatures so as to prevent subsequent chemical reactions. Thenthe porous gas permeable first electrodes 126 are deposited, followed bythe dense non-porous gas tight electrolyte members 128, followed by theporous gas permeable second electrodes 130 and finally the densenon-porous gas tight seal 138.

It is to be noted that the current collectors 135 and layers 133 of theinterconnectors 132 are integral and are arranged between the porous gaspermeable first electrodes 126 and the porous gas permeable supportstructure 116. The current collectors 135 are porous and gas permeableto allow the first reactant to flow from the porous gas permeablesupport structure 116 to the porous gas permeable first electrodes 126.The current collectors 135 collect current from/supply current to thefirst porous gas permeable first electrodes 126. The current collectors135 and layers 133 of the interconnectors 132 have high lateral, inplane, conductivity. However, it is to be noted that the currentcollectors 135 and layers 133 of the interconnectors 132 are relativelythin, of the order of a few micrometers thick. The length of the currentcollector 135 and layer 133 of the interconnector 132 is relativelylong, of the order of several mm long. Thus any leakage path is long andnarrow and leakage is minimal or substantially zero. For example eachfuel cell is about 15 mm long and about 0.030 mm thick, the currentcollector 135 and layer 133 of the interconnector 132 is almost 15 mmlong and about 1 micrometer thick. Thus the layer 133 of theinterconnector 132 is substantially gas tight for flow in a lateraldirection.

The current collectors 135 and layers 133 of the interconnectors 132comprise at least one of nickel, platinum, palladium, ruthenium andsilver, preferably two or more of these, for example nickel and platinumor nickel and palladium, nickel and ruthenium etc. The interconnectors132 also comprise yttria-stabilised zirconia to aid bonding of theinterconnector 132 to the porous barrier layer 123 and dense non-porousgas tight barrier layer 134.

A porous gas permeable current collector 131 is arranged on the porousgas permeable second electrode 130 to collect current from/supplycurrent to the second porous gas permeable second electrodes 130. Thecurrent collectors 131 have high lateral, in plane, conductivity. Thecurrent collectors 131 comprise a high conductivity metal or alloy forexample one or more of nickel and silver and one or more of platinum,palladium ruthenium and gold, for example nickel and platinum, nickeland palladium, nickel and ruthenium etc. The current collector 131 isdeposited by screen printing and doctor blading and is about 10micrometers thick.

In this example the first electrodes 26 are anode electrodes and thesecond electrodes 30 are cathode electrodes.

A cross-section through an alternative solid oxide fuel cell component212, is shown more clearly in FIGS. 10 and 11. The component 212 issubstantially the same as that shown in FIGS. 3, 4, 5 and 7 and likeparts are denoted by like numerals. The component 212 in FIGS. 10 and 11differs in that the second end 28B of each dense non-porous gas tightelectrolyte member 28 abuts and overlaps the adjacent dense non-porousgas tight interconnector 32. Additionally porous barrier layers 123 arearranged between each porous gas permeable first, anode, electrode 26and the porous gas permeable support structure 16 to prevent chemicalinteractions between the porous gas permeable anode electrodes 26 andthe porous gas permeable support structure 16.

It may be possible to deposit a porous gas permeable barrier layer overthe whole surface of the porous gas permeable support structure toprevent chemical interactions between the porous gas permeable supportstructure and the porous gas permeable first electrodes. A densenon-porous gas tight barrier layers is subsequently provided atappropriate positions over the porous gas permeable barrier layer forthe interconnectors. The dense non-porous gas tight peripheral seal isprovided over the remaining surface of the porous gas permeable supportstructure.

The prevention of the leakage of the reactant from the first electrodesto the second electrodes is very important because otherwise thereactants, hydrogen and oxygen, would mix and burn and lead to damageand loss of performance of the fuel cells.

Although the invention has been described with reference to a densenon-porous gas tight seal around the second electrodes it may in somecircumstances be possible to dispense with the dense non-porous gastight seal if the encapsulation of first electrodes is completelyprevented.

Although the invention has been described the first electrodes as anodeelectrodes it may be possible that the first electrodes are cathodeelectrodes.

The reactant supplied to the anode is generally hydrogen or the productsof reformation of a hydrocarbon fuel, for example hydrogen, carbondioxide, carbon monoxide. The reactant supplied to the cathode isgenerally oxygen, air or other oxygen containing gas.

The arrangement of the fuel cells enables the dense non-porous gas tightlayers to be deposited initially and fired at the highest temperaturesto obtain the sintering to form the dense non-porous gas tight layers.The other layers are deposited and fired at progressively lowertemperatures. This enables the solid oxide fuel cells to operate attemperatures up to 1200° C.

The length and thickness of the layers of the solid oxide fuel cellstack are important design variables and influence the solid oxide fuelcell stack performance. Current collection losses are minimised byminimising the length of any current path. This is achieved byminimising the pitch of the solid oxide fuel cells. The pitch of thesolid oxide fuel cells is length of the electrolyte member plus thelength of the interconnector. Resistance to flow of current is minimisedby minimising the number of interfaces. These conflicting requirementsresult in an optimum solid oxide fuel cell pitch, the magnitude of whichdepends upon the thickness and conductivity of the anode and cathodecurrent collectors. The pitch of solid oxide fuel cell is between 5 mmand 20 mm.

The electrolyte member/interconnector aspect ratio, the ratio of thelength of the electrolyte member to the length of the interconnector,should be maximised. This is because the longer the interconnector, themore expensive material is contained in the solid oxide fuel cell stackand the longer the support structure becomes the power density isreduced. Maximising the aspect ratio maximises the current densitythrough the interconnectors. This makes the solid oxide fuel cell stackperformance sensitive to electrode-interconnector contact resistance andto interconnector conductivity. An electrolyte member to interconnectoraspect ratio of about 3 to 1 is used.

1-43. (canceled)
 44. A method of manufacturing a solid oxide fuel cellcomponent comprising a porous gas permeable support structure having asurface; at least first, second and third solid oxide fuel cells beingarranged in spaced apart relationship on the surface of the porous gaspermeable support structure, such that the first cell is adjacent to thesecond cell, the second cell is adjacent to the third cell, and thecells are arranged in electrical series; the first, second and thirdcells each comprising a dense non-porous gas tight electrolyte member, aporous gas permeable anode, and a porous gas permeable cathode; theanode of the first cell being connected to the cathode of the adjacentsecond cell by a first dense non-porous and gas tight interconnector;the first interconnector having a bottom surface contacting the surfaceof the support, a first side surface contacting the anode of the firstcell, a top surface, and a second side surface spaced apart from theanode of the second cell; the anode of the first cell contacting aportion of the top surface of the first interconnector and the cathodeof the second cell contacting another portion of the top surface of thefirst interconnector; the anode of the second cell being connected tothe cathode of the adjacent third cell by a second dense non-porous andgas tight interconnector; the second interconnector having a bottomsurface contacting the surface of the support, a first side surfacecontacting the anode of the second cell, a top surface, and a secondside surface spaced apart from the anode of the third cell; the anode ofthe second cell contacting a portion of the top surface of the secondinterconnector and the cathode of the third cell contacting anotherportion of the top surface of the second interconnector; and theelectrolyte member of the second cell being arranged between the anodeand cathode of the second cell, a first end of the electrolyte member ofthe second cell contacting the surface of the support between the secondside surface of the first interconnector and a side surface of the anodeof the second cell, a second end of the electrolyte member of the secondcell contacting the top surface of the second interconnector between theanode of the second cell and the cathode of the third cell, and theelectrolyte member of the second cell is spaced apart from the cathodeof the third cell by a portion of the top surface of the secondinterconnector, the method comprising the steps of: (a) forming theporous gas permeable support structure; (b) depositing the denseinterconnectors on the porous gas permeable support structure; (c)depositing the anodes on the porous gas permeable support structure; (d)depositing the dense non-porous gas tight electrolyte members on theanodes; and (e) depositing cathodes on the dense non-porous gas tightelectrolyte members.
 45. The method according to claim 44, furthercomprising depositing a dense non-porous gas tight peripheral seal layersuch that the peripheral seal layer covers at least a portion of thesurface of the support structure not covered by the anodes, theinterconnectors and the electrolyte members.
 46. The method according toclaim 45, wherein step (d) comprises depositing the dense non-porous gastight electrolyte members on the anodes such that the dense non-porousinterconnectors, the dense non-porous gas tight peripheral seal layerand the dense non-porous gas tight electrolyte members are arranged toencapsulate all of the anodes except for the surfaces of the anodesfacing the surface of the porous gas permeable support structure toreduce leakage of reactant from the anodes.
 47. The method according toclaim 44, further comprising (f) depositing a dense non-porous sealaround the cathodes such that the dense non-porous gas tight electrolytemembers and the dense non-porous seal encapsulate at least one of thecathodes except for the surface of at least one cathode remote from thedense non-porous gas tight electrolyte members to reduce leakage ofreactant from the at least one cathode.
 48. The method according toclaim 47, wherein step (f) comprises depositing the dense non-porousseal around the cathodes such that the dense non-porous gas tightelectrolyte members and the dense non-porous seal encapsulate all thecathodes except for the surfaces of the cathode remote from the densenon-porous gas tight electrolyte members to reduce leakage of reactantfrom the cathode.
 49. The method according to claim 44, furthercomprising depositing a dense non-porous gas tight seal in an areadefined by a side surface of the electrolyte member of the second cell,a side surface of the cathode of the second cell, a side surface of thecathode of the third cell, and the top surface of the secondinterconnector to reduce leakage of reactant.
 50. The method accordingto claim 49, wherein the electrolyte member of the second cell and thedense non-porous gas tight seal are arranged to encapsulate the cathodeof the second cell except for surfaces of a cathode remote from theelectrolyte member of the second cell to reduce leakage of reactant fromthe cathode.
 51. The method according to claim 44, further comprisingproviding a current collector and a porous barrier layer such that eachof the anodes is arranged in contact with the surface of a currentcollector, each current collector being arranged in contact with aporous barrier layer, the porous barrier layer being arranged in contactwith the surface of the porous gas permeable support structure.
 52. Themethod according to claim 44, wherein the first, second and thirdinterconnectors each comprises a first layer on the porous gas permeablesupport structure, a second layer on the first layer, and a third layeron the second layer, the first layer is dense, non-porous gas tight andis electronically and ionically non-conducting, the second layer bondsthe third layer to the first layer and the third layer is electronicallyconducting.
 53. The method according to claim 52, wherein the firstlayer comprises a ceramic, the second layer comprises lanthanum chromiteand the third layer comprises a metal.
 54. The method according to claim52, wherein the third layer comprises nickel, platinum, palladium,ruthenium and silver.
 55. The method according to claim 52, wherein thefirst layer comprises yttria stabilized zirconia doped with silicateglass or yttria stabilized zirconia doped with calcium chromate.
 56. Themethod according to claim 44, wherein the first, second and thirdinterconnectors each comprises a first layer on the porous gas permeablesupport structure and a second layer on the first layer, the first layeris dense non-porous and is electronically and ionically nonconductingand the second layer is electronically conducting.
 57. The methodaccording to claim 56, wherein the first layer comprises a ceramic andthe second layer comprises a metal.
 58. The method according to claim56, wherein the second layer comprises nickel, platinum, palladium,ruthenium, silver.
 59. The method according to claim 56, wherein thefirst layer comprises yttria stabilized zirconia.
 60. The methodaccording to claim 56, wherein the first layer comprises yttriastabilized zirconia doped with silicate glass or yttria stabilizedzirconia doped with calcium chromate.
 61. The method claim 51 wherein anelectronically conducting layer of each of first, second and thirdinterconnectors is integral with the current collector.
 62. The methodaccording to claim 44, further comprising arranging a porous gaspermeable barrier layer between each of the anodes and the surface ofthe porous gas permeable support structure to prevent chemicalinteractions between the anodes and the porous gas permeable supportstructure.
 63. The method according to claim 44, further comprisingproviding a dense non-porous gas tight peripheral seal extending arounda periphery of an area defined by the anodes and the dense non-porousinterconnectors.
 64. The method according to claim 63, wherein ends ofat least one dense non-porous interconnector contacts a top surface ofthe dense non-porous gas tight peripheral seal.
 65. The method accordingto claim 64, wherein edges of the dense non-porous gas tight electrolytemembers contact a top surface of the dense non-porous gas tightperipheral seal.
 66. The method according to claim 63, wherein the densenon-porous gas tight peripheral seal comprises a first layer and asecond layer.
 67. The method according to claim 63, wherein the densenon-porous gas tight peripheral seal comprises a ceramic.
 68. The methodaccording to claim 63, wherein the dense non-porous gas tight peripheralseal comprises yttria stabilized zirconia.
 69. The method according toclaim 63, wherein the dense non-porous gas tight peripheral sealcomprises yttria stabilized zirconia doped with silicate glass or yttriastabilized zirconia doped with calcium chromate.
 70. The methodaccording to claim 44, further comprising providing a dense non-porousgas tight peripheral seal member covering at least a portion of thesurface of the support structure not covered by the anodes, theinterconnectors and the electrolyte members and a dense non-porous gastight seal comprising a seal layer filling an area defined by a sidesurface of the electrolyte member of the second cell, a side surface ofthe cathode of the second cell, a side surface of the cathode of thethird cell, and the top surface of the second interconnector, whereinthe dense non-porous seal contacts a top surface of the dense non-porousgas tight peripheral seal.
 71. The method according to claim 70, whereinthe dense non-porous seal contacts the top surface of the electrolytemember of the second cell.
 72. The method according to claim 70, whereinthe dense non-porous gas tight seal comprises a glass ceramic material.73. The method according to claim 44, wherein a portion of the first endof the electrolyte member of the second cell contacting a top surface ofthe first interconnector.
 74. The method according to claim 73, whereinthe first end of the electrolyte member of the second cell contacts thesecond side of the first.
 75. The method according to claim 52, whereinthe third layer comprises an alloy of any two or more of nickel,platinum, palladium, ruthenium and silver.
 76. The method according toclaim 52, wherein the second layer comprises an alloy of any two or moreof nickel, platinum, palladium, ruthenium, and silver.